Fail-safe rotary actuator for a coolant circuit for preventing damages to an internal combustion engine as a result of inadequate cooling capacity when the rotary actuator fails.
Such rotary actuators are preferably used for providing an emergency operation of the coolant circuit of an internal combustion engine in the event coolant controlled by the rotary actuator is no longer sufficient to reliably cool the internal combustion engine as result of a malfunction of the rotary actuator.
DE 102 43 778 A1 discloses an actuating device with an electromotive rotary drive, via which an actuating element, in particular a rotary slide of a rotary-slide valve can be driven rotatably about an axis of rotation between a first end position and a second end position and can be acted upon out of the first end position by a spring. The electromotive actuating drive is hereby designed as reversing drive and the spring action upon the actuating element is effective only between the first end position and an intermediate position, with the intermediate position lying between the first end position and the second end position. In the event the actuating element designed as a rotary-slide valve is a regulating valve in a coolant circuit of an internal combustion engine, the rotation of the actuating element as a result of the spring action upon the actuating element maintains a cooling of the internal combustion engine during emergency operation, when the electromotive rotary drive fails.
The disclosed actuating device is, however, disadvantageous because the emergency operation is triggered immediately after failure of the rotary drive as a result of the constantly present spring action upon the actuating element. As a consequence, depending on the ambient temperature, motor load, and travel speed, the coolant can no longer heat up to the operating temperature, causing the internal combustion engine to run less efficient during emergency operation.